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SubjectRe: [PATCH V5] powercap/drivers/idle_injection: Add an idle injection framework
On Wed, Jun 06, 2018 at 03:42:08PM +0200, Daniel Lezcano wrote:
> On 06/06/2018 14:23, Peter Zijlstra wrote:
> > On Tue, Jun 05, 2018 at 11:16:40AM +0200, Daniel Lezcano wrote:
> >> + atomic_t idle_duration_ms;
> >> + atomic_t run_duration_ms;
> >
> >> + idle_duration_ms = atomic_read(&ii_dev->idle_duration_ms);
> >
> >> + run_duration_ms = atomic_read(&ii_dev->run_duration_ms);
> >
> >> + atomic_set(&ii_dev->run_duration_ms, run_duration_ms);
> >> + atomic_set(&ii_dev->idle_duration_ms, idle_duration_ms);
> >
> >> + *run_duration_ms = atomic_read(&ii_dev->run_duration_ms);
> >> + *idle_duration_ms = atomic_read(&ii_dev->idle_duration_ms);
> >
> >> + if (!atomic_read(&ii_dev->idle_duration_ms))
> >
> >> + if (!atomic_read(&ii_dev->run_duration_ms))
> >
> > What is the point of atomic_t here ?!
>
> idle_duration and run_duration can be changed from different places at
> the same time. The atomic is here to ensure the read/write are consistent.
>
> Do you think it is pointless ?

Yes, atomic_read() / atomic_set() are no more atomic than READ_ONCE() /
WRITE_ONCE().

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